1. Field of the Invention
The present invention relates to a sealing arrangement between members in close contact with each other, and to a longitudinally-endless gasket mounted in a groove portion formed in one of the members to provide sealing between this one member and another of the members when they are fastened to each other.
For example, the present invention relates to a sealing arrangement between an intake manifold and a cylinder head in an engine mounted to an automobile or the like.
To put it more concretely, the invention relates to a longitudinally-endless gasket mounted in a groove portion formed in a face of an intake manifold disposed to face a cylinder head of an engine. The face of the intake manifold in which the groove portion is formed also faces the cylinder head of the engine. When the intake manifold and the cylinder head are fastened to each other, the longitudinally-endless gasket mounted in the groove portion provides sealing therebetween.
2. Description of the Related Art
As a longitudinally-endless gasket mounted in a groove portion formed in one of members to provide sealing between this one member and another of the members when they are fastened to each other, there is a known gasket for providing sealing between an intake manifold and a head member of an engine mounted to an automobile or the like.
Conventionally, as a gasket for providing sealing between an intake manifold and a head member of an engine mounted to an automobile or the like, a rubber gasket made of an elastic body such as synthetic rubber and having a rectangular or oval sectional shape is used.
The rubber gasket for the intake manifold is inserted into a groove portion formed in a face of the intake manifold facing the cylinder head during a mounting operation process. At this time, many portions of the rubber gasket are inserted into the groove portion and a tip end side is exposed from the groove portion. A face of the tip end side exposed from the groove portion is brought into contact with the cylinder head during a succeeding tightening operation. When the intake manifold and the cylinder head are fastened to each other during this tightening process, the rubber gasket is brought into close and tight contact with inner walls of the groove portion of the intake manifold and the cylinder head through compressive elastic deformation, thereby a required sealing operation can be obtained. Fastening of the intake manifold and the cylinder head to each other during the tightening process is normally performed by using fasteners such as bolts disposed in a vicinity of the groove portion.
In such a prior-art rubber gasket, there were problems such as incomplete insertion of the gasket into the groove portion during an operation process of mounting the gasket into the groove portion of the intake manifold, and falling of the rubber gasket during the tightening process.
In other words, to describe it by referring to the drawings, as shown in FIG. 11, a prior-art gasket for the intake manifold, e.g., a rubber gasket 1 formed of an elastic body such as synthetic rubber or the like is formed into a shape of a thin O-ring having an oval sectional shape which is long in a vertical direction to meet a recent demand for weight reduction. Such a rubber gasket 1 has a poor shape maintaining property because of its thin shape. Therefore, it is difficult to quickly and reliably insert the gasket during an operation process of mounting the gasket within the groove portion 21 of intake manifold 2. After inserting the rubber gasket 1 into the groove portion 21, a tightening operation for fastening the intake manifold 2 and cylinder head 3 in directions shown with arrows 101 and 102 is performed at a tightening torque of about 4.9 MPa to 9.8 MPa by using fasteners such as bolts or the like disposed in a vicinity of the groove portion. During this tightening process, because the rubber gasket 1 is in the shape of an O-ring having an oval sectional shape which is long in the vertical direction, the gasket 1 is likely to be displaced outwardly from the groove portion 21 and to fall diagonally relative to a fastening direction.
In a normal assembly line of an engine of an automobile, after the rubber gasket 1 is mounted into the groove portion 21 of the intake manifold 2, a mounting face of the intake manifold 2 is turned around into a state shown in FIG. 11. Then, an operation for tightening the intake manifold 2 and the cylinder head 3 against each other is performed.
If structure, such as elastic projecting portions 22a, 22b, and the like, provided on opposite side faces of the rubber gasket 1 facing opposite inner wall faces of the groove portion 21, for preventing the rubber gasket 1 from falling, is insufficient, the rubber gasket 1 falls from the groove portion 21 during turning of the intake manifold 2, an inserted position is displaced to cause poor sealing, or more serious damage is caused in some cases.
If large structure for preventing falling of the rubber gasket 1 is provided in order to cope with the above problems, it becomes difficult to insert the rubber gasket 1 into the groove portion 21.
Therefore, a gasket which has excellent workability such that mounting and tightening operations can be performed easily and which can be reliably mounted is required.
Because the gasket for the intake manifold, formed into a shape of a thin O-ring having an oval sectional shape which is long in the vertical direction to meet the recent demand for weight reduction, is likely to fall when it is subjected to strong tightening, a compression rate is set at a low value to cope with this problem. However, low tightening for which the compression rate is set at a low value exerts a considerable bad influence on a sealing property.
The before described problems of the gasket for the intake manifold of the engine mounted to the automobile or the like are common to a longitudinally-endless gasket (e.g., a rocker cover gasket, a front cover gasket, an oil pan gasket, a timing chain cover gasket, and the like) mounted within a groove portion formed in one of members to provide sealing between this one member and another of the members when they are fastened to each other.
In view of the above-described problems of the longitudinally-endless gasket for providing sealing between one member and another of the members when they are fastened to each other, it is an object of the present invention to provide a gasket which has excellent workability such that mounting and tightening operations can be performed easily and which can exert satisfactory sealing performance.